Field of Invention
The present invention relates to a high-speed precision interrupted ultrasonic vibration cutting method. By imparting ultrasonic vibration to a cutting tool through interrupted ultrasonic cutting during a whole cutting process, with reasonable set cutting parameters and vibration parameters, a workpiece is accomplished. An ultrasonic separation effect, which occurs during the cutting process, is able to realize precision machining in a high cutting speed.
Description of Related Arts
A high-speed cutting technology is an advanced machining technology having higher efficiency. Compared to a traditional cutting technology, the high-speed cutting technology obtains a much higher cutting speed. Non-ferrous metal, cast iron, steel, fiber reinforced composite material and nearly all kinds of difficult-to-machine materials are able to be machined. The high speed range differs for different materials. Steel, cast iron, nickel base alloys, titanium alloys, aluminum alloys, bronze and brass, and fiber-reinforced plastics are tested by Institut für Produktionsmanagement, Technologie und Werkzeugmaschinen (PTW) of Darmstadt University of Technology, Germany, in 1980s, and cutting speed ranges thereof are showed in FIG. 1.
Ultrasonic vibration cutting is a typical interrupted cutting method and is gradually developed into an advanced high precision machining method after being proposed. The conventional ultrasonic vibration cutting method (referring to FIG. 2A) has the vibration direction in parallel with the cutting speed direction and thus is known as the longitudinal ultrasonic vibration cutting method. The conventional ultrasonic vibration cutting method has advantages of reducing the cutting force and the cutting temperature, and improving the cutting ability and the machining quality. However, during the cutting process, the tool tip keeps engaged in the finished surface even though a separation effect between the tool tip and the chip exists, which enhances the friction between the cutting edge and the finished surface and causes tool breaking. The elliptical ultrasonic vibration cutting method is proposed in the 1990s, which realizes the complete separation of the tool and the workpiece because of the periodical elliptical vibration of the cutting tool. Besides, the cutting force and the machining error are further reduced compared to the conventional ultrasonic vibration cutting method, and the tool life is prolonged by more than ten times. However, a critical cutting speed v=2πFA (F is the tool vibration frequency, and A is the tool vibration amplitude) exists in both of the conventional ultrasonic vibration cutting method and the elliptical ultrasonic vibration cutting method. Therefore, the above significant advantages are realized at an extremely low cutting speed (generally 4-6 m/min). Once the cutting speed approaches to or exceeds the critical cutting speed, the advantages are all vanished. In conclusion, the application of ultrasonic vibration cutting is largely limited.